The present invention relates to a method of controlling a fuel injection and an apparatus therefor, and more particularly to a method of and an apparatus for controlling a fuel injection suitable for an engine of an automobile so as to optimize an air-fuel ratio for the engine during acceleration and deceleration of the automobile.
It is general practice in a fuel injection type internal combustion engine to calculate a fuel injection quantity on the basis of both intake-pipe absolute pressure and engine speed or both intake-air quantity and engine speed and to equally add a predetermined output incremental value to the calculated fuel injection quantity when a throttle valve of the engine has an opening amount more than its intermediate opening amount, e.g., 30.degree. or more, thereby to obtain a necessary output.
When the above-mentioned output incremental value is excessively large, however, the output change becomes so large as to cause a shock. On the other hand, if the output incremental value is set to be relatively low in order to prevent such shock, it may not be possible to obtain excellent engine responsiveness during acceleration.
The above-described fuel injection type internal combustion engine includes such a type of engine that the air-fuel ratio for the engine is controlled to the leaner side for the purpose of reduction in fuel cost when the throttle valve has a small opening amount, e.g., 30.degree. or less and after the engine has been completely warmed up. When an output air-fuel ratio, at which the maximum output torque is obtained, is obtained in such internal combustion engine by effecting the output incremental correction as described above, the air-fuel ratio quickly changes from a lean air-fuel ratio, e.g., 22 to the output air-fuel ratio, e.g., 12.5. Accordingly, when the throttle valve changes its open position from a small opening amount to an intermediate opening amount, a shock is caused which is unpleasant to the driver. It is to be noted that when the throttle valve changes its open position from a small opening amount to a large opening amount, the driver himself has the intention of sudden acceleration. Therefore, any shock resulting from the acceleration will not make the driver feel unpleasant.